There are a wide variety of self-cleaning threaded nuts in which the top and bottom faces of the nut have been machined to form an interruption of the threads which allows the nut to clean adjacent threads while turning in either direction.
For example, the U.S. Patent to Pease No. 2,091,274 discloses a thread cleaning nut in which the top and bottom faces of the nut have been machined to form an interruption of the threads which provides for cleaning of adjacent threads.
The U.S. Patents to Crawford No. 3,896,495, Lanius, Jr., 3,501,995, and Paquette 561,913 are further examples of nuts having thread cleaning features.
Other U.S. patents of a more general interest are the U.S. Patents to Schrader No. 1,347,124, Thomas, No. 1,447,578 and Gutensohn No. 2,562,032.
One of the problems with conventional thread cleaning nuts is the number of machine cuts required to produce the thread cutting feature. For example, in the above-noted Pease patent, at least three machine cuts are required, 12 if both faces of the nut are included.
The nut of the Paquette patent requires three straight cuts and three curved cuts. The relatively large number of machine cuts typically makes the product impractical to mass-produce.
Another problem with the prior art is that the end face of the machined nut has a relatively small percentage still intact and what is left is not continuous so that the thread cleaning features may be crushed if the threads are over tightened.
One way to overcome this problem is to make the nut from a harder steel. However, this increases production costs even more. A larger face is desirable since it increases the chance of the nut staying tight in constant pressure motion areas, such as on an engine of an automobile or on heavy equipment.
Another problem generally associated with the prior art is that so many of the designs are not practical and, thus, a relatively hard material must be used for the nut. For example, without harder material, the thread cutting mechanisms of many such designs have a tendecy of breaking off or may get jammed on a dirty or rusty bolt.